Immunity to schistosomes: progress toward vaccine.

Among the major parasitic infections, schistosomiasis may be the most promising candidate for human vaccination. Information about mechanisms of immunity, gained mainly from experimental models but likely to be relevant to human infection, indicates a dynamic balance between protective and regulatory (blocking) mechanisms. Besides cell-mediated responses leading to macrophage activation, antibody-dependent cell-mediated cytotoxicity systems involving precise antibody isotypes and nonlymphoid cells (mononuclear phagocytes, eosinophils, and platelets) appear to be essential effectors of immune attack. The slow development of immunity in humans seems related to the production of antibodies that cross-react with schistosomulum surface antigen and block the binding of antibodies of the effector isotype. Schistosomes that survive in the bloodstream and produce chronic infections may evade the immune system as a result of intrinsic changes in membrane susceptibility and of transient expression of target antigens; at other stages of the parasite life cycle, cross-reactive molecules may be secreted that play an essential role in the induction of immunity. Several schistosome proteins have been characterized as candidates for vaccination. Among these, an antigen of 28 kilodaltons has been cloned and shown to be immunogenic in humans and protective in mice, rats, and baboons.

A high proportion of donor CD4+ T cells expressing the lymph node-homing chemokine receptor CCR7 increases incidence and severity of acute graft-versus-host disease in patients undergoing allogeneic stem cell transplantation for hematological malignancy.

CC-chemokine receptor 7 (CCR7), a chemokine receptor required for transmigration into lymphoid organs, is only expressed by naive and central memory T cells. T cells with a capacity of homing into lymphoid organs can initiate acute graft-versus-host disease (GVHD) in mice and respond vigorously in vitro to alloantigens in humans, but their impact on clinical outcomes is unknown. We evaluated prospectively the distribution of naive, central memory and CCR7neg memory T-cell subsets in 39 bone marrow and 23 granulocyte colony-stimulating factor-mobilized peripheral blood stem cell allografts and investigated their impact on patient outcomes. Ranges of the relative proportions of CCR7+ cells within CD4+ and CD8+ T-cell populations were broad, but did not differ between the two sources of allografts. By multivariate analysis, high percentage of donor-derived CD4+CCR7+ T cells (>73.5%) significantly correlated with incidence, earliness of onset and severity of acute GVHD, conferring the highest adjusted hazard ratio (HR=3.9; 95% confidence interval 1.4-10.8; P=0.008) without interfering in other clinical events, especially chronic GVHD and relapse. Determination of the percentage of CD4+CCR7+ T cells in the graft provides a predictive indicator of acute GVHD. Partial depletion of this subset may reduce the risk of acute GVHD while preserving immunotherapeutic effects.

[3H]serotonin release: an improved method to measure mast cell degranulation.

A method based on the release of tritium-labelled serotonin by activated mast cells in rodents is described. Mast cells incorporate labelled serotonin selectively and release the label after activation by non-specific stimulators (compound 48/80, polymyxin B sulphate, ATP, bovine chymotrypsin and L-alpha-lysophosphatidylcholine) or anaphylactic antibody and the corresponding antigen. These two types of activation were investigated in comparison with the toluidine blue microscopic rat mast cell degranulation test, and a methodological study of the release of [3H]serotonin is described. The measurement of labelled serotonin release provides a simple and quick assay of mast cell degranulation compared to the time required for the classical rat mast cell degranulation technique and achieves a greater sensitivity.

Hepatitis B circulating immune complexes. Characterization by radioimmunoprecipitation--PEG assay (RIPEGA).

Incidence of circulating immune complexes (IC) was investigated in carriers of hepatitis B antigen (HBAg) and/or anti-HB antibodies (anti-HBAb). Three methods were used: radiolabelled C1q binding test (C1qBT), complement fixation test (CFT), and optical density (OD) measurement after dissolution of 3% polyethylene glycol (PEG) precipitate of serum. A highly significant correlation was obtained between these three techniques. The level of IC was higher in carriers of HBAg without anti-HBAb, than in others. The characterization of HBAg and anti-HBAB in IC was carried out by a new procedure, the radioimmunoprecipitation-PEG assay (RIPEGA), This sensitive and reproducible test was performed by incubation of 125I-HBAg or 125I-HBAG with 3% precipitate of the carriers' sera. Separation of free from complexed 125I-HBAg or 125I-HBAb was achieved by PEG precipitation. A highly significant correlation was found between the levels of circulating IC evaluated by the C1q-BT and the quantities of HBAg or anti HBAb measured by RIPEGA. RIPEGA was used to quantify HBAg and anti-HBAb present in serum from HBAg and/or anti-HBAb carriers, confirmed by a radioimmunoassay. In preliminary results, RIPEGA was shown to be more sensitive than classical radioimmunoassay.

Improved permeabilization procedure for flow cytometric detection of internal antigens. Analysis of interleukin-2 production.

A cell membrane permeabilizing treatment is described which involves the use of lysolecithin at low concentration in acidic acetate buffer and paraformaldehyde fixation. It preserved well-separated scatter cytograms of small and large lymphocytes. The accuracy of the immunochemical detection of internal antigens by flow cytofluorography was demonstrated by the linear relationship between the percentage of fluorescent cells detected and the proportion of intracellular antigen-containing cells in mixtures with antigen-negative cell lines. Cell cycle analysis by dual nuclear staining with propidium iodide and FITC-conjugated Ki-67 antibody recognising in vitro stimulated human T lymphocytes verified that the proliferating lymphocytes retained their increased light scatter properties after permeabilization. Enumeration of interleukin-2 (IL-2) producing cells by their cytoplasmic immunofluorescence showed that enlarged lymphocytes were the main IL-2 producing cells. This improved permeabilization procedure, by gating small and enlarged lymphocytes separately, makes it possible to determine by two color fluorescence the immunophenotype of activated T cells committed to interleukin production.

Recall response to cytomegalovirus in allograft recipients: mobilization of CD57+, CD28+ cells before expansion of CD57+, CD28- cells within the CD8+ T lymphocyte compartment.

BACKGROUND: Strong correlations have been described between persistently elevated proportions of CD57+ (CD28-) CD8+high T lymphocytes and cytomegalovirus (CMV) infection, in healthy individuals as well as in transplant patients. We investigated whether secondary exposure to CMV triggers recall responses within the CD8 T cell compartment. METHODS: In a longitudinal study in 123 kidney recipients, we compared 17 primary CMV infections with 27 secondary CMV infections. Subset composition of the CD8 compartment was analyzed by flow cytometry. RESULTS: CD8 lymphocytosis occurred significantly earlier (by 17 days on average) in CMV reactivations than in primary infections. Both in primary and secondary infections, CD28+ CD8+high T lymphocytes were mainly recruited at the start. In formerly CMV-seropositive patients, preexisting CD57+ CD8+high T lymphocytes switched at the start from no expression of CD28 to high expression of CD28 and, concomitantly, from CD45RA to high expression of CD45RO. These cells reverted rapidly to a CD28- and CD45RA+ phenotype. Nevertheless, the accumulation of CD57+ (CD28-) CD8+high T cells was delayed similarly in primary and secondary CMV infection, progressing over a period between 2 and 8 weeks after the onset of CD8 lymphocytosis to plateau at 366 CD57+ CD8+high cells/ mm3 on average. CONCLUSIONS: The faster kinetics of CD8 lymphocytosis in secondary CMV infection suggests that a recall response triggers cycling "memory" cells within the CD28+ CD8+high subset, while preexistent CD57+ CD8+high T cells with a long-lived cell phenotype can also be mobilized, possibly through the transient acquisition of CD28 expression. The protracted accumulation of CD57+ (and CD28-) lymphocytes might then reflect an end-stage differentiation.

Enhancing the effect of secreted cyclophilin B on immunosuppressive activity of cyclosporine.

BACKGROUND: Cyclophilin B (CyPB) is a cyclosporine (CsA)-binding protein, located within intracellular vesicles and secreted in biological fluids. In previous works, we reported that CyPB specifically interacts with the T-cell membrane and potentiates the ability of CsA to inhibit CD3-induced proliferation of T lymphocytes. METHODS: CyPB levels were measured in plasma from healthy donors and transplant patients. The role of extracellular CyPB on the distribution and activity of CsA was investigated first by studies on the uptake of free and CyPB-complexed drug by blood cells, and second by studies on the inhibitory effects of these two compounds on the CD3-induced proliferation of peripheral blood mononuclear cells. RESULTS: A significant increase in plasma CyPB level was observed for CsA-treated patients (13+/-6.4 nM, n=42) in comparison with untreated donors (4.3+/-2.1 nM, n=34). In vitro, extracellular CyPB dose dependently modified CsA distribution between plasma, erythrocyte, and lymphocyte contents, by both retaining the complexed drug extracellularly and promoting its specific accumulation within peripheral blood mononuclear cells. Moreover, the enhanced ability of CyPB-complexed CsA to suppress CD3-induced T-cell proliferation was preserved in the presence of other blood cells, implying specific targeting of the drug to sensitive cells. Furthermore, although a large interindividual variability of sensitivity to the drug was confirmed for 18 individuals, we found that CyPB potentiated the activity of CsA in restoring a high sensitivity to the immunosuppressant. CONCLUSION: These results suggest that plasma CyPB may contribute to the acceptance and the good maintenance of organ transplantation by enhancing the immunosuppressive activity of CsA through a receptor-mediated incorporation of CyPB-complexed CsA within peripheral blood lymphocytes.

Implication of cyclosporine in up-regulation of Bcl-2 expression and maintenance of CD8 lymphocytosis in cytomegalovirus-infected allograft recipients.

T cell homeostasis and CD4/CD8 ratios are normally reestablished by apoptotic clearance of activated T cells after immune stimulation. In allograft recipients with cytomegalovirus infection, CD8 lymphocytosis persists after negativation of viral cultures, contrary to immunocompetent hosts. We investigated the expression of Bcl-2 protein, an intracellular suppressor of apoptosis, and of CD95 (APO-1/Fas), a membrane inducer of apoptosis, in peripheral blood lymphocytes from 45 solid organ recipients. During the viremic phase of CMV infection, we found absence or diminished expression of Bcl-2 protein and increased expression of CD95 antigen in activated CD8+ T cells. Opposite evolution of these molecular regulators of apoptosis was reflected by the presence of 10-25% of apoptotic lymphocytes with fragmented DNA, as shown by both in situ nick translation and electrophoresis. Normalization of Bcl-2 expression was progressive over several months but still lower than in uninfected allograft recipients. These results suggest that the initial evolution of CMV infection in allograft recipients resembles acute viral infection in immunocompetent hosts. Conversely, we showed that overexpression of Bcl-2 protein in lymphocytes from uninfected allograft recipients, and culture of unstimulated normal lymphocytes with 0.5 micrograms/ml cyclosporine led to an increase in the expression of intracellular Bcl-2. This up-regulation of Bcl-2 protein by cyclosporine suggests the acquisition of resistance to apoptosis. Thus, the reversion of balance between T cell death and survival after acute CMV infection might be impeded by cyclosporine. Combination of CMV latent infection and cyclosporine therapy appears therefore critical to shift the homeostatic maintenance of the peripheral lymphocyte compartment toward persistingly high numbers of CD8+ T cells.

Improvement in the outcome of rejection with pentoxifylline in renal transplantation: a randomized controlled trial.

BACKGROUND: Pentoxifylline (PTX), a methylxantine phosphodiesterase inhibitor commonly used to treat peripheral vascular disease, has been shown to decrease the production of proinflammatory cytokines and reactive oxygen species and to reduce the toxic effects of cyclosporine. Thus, administration of PTX to transplant patients, as an adjunct to immunosuppressive therapy, could prevent numerous posttransplantation complications. METHODS: One hundred forty consecutive patients receiving cadaveric kidney grafts were registered in a randomized double-blind study comparing PTX at a dose of 800 mg/day, then 1200 mg/day, versus placebo during the first 6 months after transplantation. All patients were followed up for 1 year. RESULTS: Rejection episodes were validated as the only independent risk factor for graft loss in this study. We compared graft survival rates in each group according to the presence or absence of acute rejection. Acute rejection reduced graft survival in the control group (graft survival rate at 1 year, 59% vs. 97%, P < 0.001), but this adverse effect was blunted in the PTX group (72% vs. 89%, NS). This improvement was confirmed by multivariate analysis for risk factors, with graft survival rates being described at best as the interaction between rejection and treatment (PTX vs. placebo, P = 0.045). CONCLUSION: Although PTX does not modify the incidence of any posttransplant complications, it weakens the consequences of rejection on graft survival.

Immunomodulatory effect of pentoxifylline during human allograft rejection: involvement of tumor necrosis factor-alpha and adhesion molecules.

BACKGROUND: Pentoxifylline (PTX), a methylxanthine phosphodiesterase inhibitor, is poorly active as an immunosuppressant but prevents the synthesis of proinflammatory cytokines. In a randomized double-blind study comparing PTX versus placebo in 140 patients receiving cadaveric kidney grafts under cyclosporine and prednisone, we have shown that PTX weakened the consequences of rejection on graft survival. To assess the mechanism underlying the beneficial effect recorded during this trial, we analyzed the impact of PTX on tumor necrosis factor (TNF-alpha) production and expression of cell adhesion molecules. METHODS: Plasma levels of TNF-alpha and its soluble receptors (sTNF-RI, sTNF-RII) and of soluble vascular cell adhesion molecule 1 (sVCAM-1) were monitored over the 6 months postgraft period when PTX or placebo were administered. Expression of VCAM-1 and intercellular cell adhesion molecule 1 was scored by immunohistochemical staining of biopsy specimens from patients who underwent rejection crisis. Lymphocyte subset composition was analyzed longitudinally during cytomegalovirus (CMV) infections. RESULTS: Plasma TNF-alpha levels were significantly reduced in the PTX-treated group over the 6 months of administration, and specifically during isolated rejection episodes and during CMV infections. Plasma levels of sTNFR-I, sTNFR-II, and sVCAM-1 did not differ between the two groups of patients, but a decrease in renal tubular VCAM-1 expression was observed in the PTX group. During CMV infections, CD8 lymphocytosis and expansion of CD57+ (CD28-) CD8+ T cells were similar in the two groups. CONCLUSION: The data collected during this double-blind study point to an immunomodulatory role of PTX, the beneficial effect on graft survival resulting from a restraining effect of the drug on the inflammatory conditions involved in acute graft rejection.

Negative immunohistochemical detection of CD103 (alphaEbeta7 integrin) in the infiltrates of acute rejection in liver and kidney transplantation.

BACKGROUND: The infiltration of epithelium by CD8+ T lymphocytes in human renal or liver allografts is a critical feature of acute rejection. CD103 expression can be acquired in vitro by CD8+ cytotoxic T lymphocytes in response to allogeneic renal epithelial cells and promotes their adhesion to epithelium and subsequent lysis of epithelial cells. We investigated the expression of CD103 in T-cell infiltrates during acute renal or liver rejection (grade < III). METHODS: Immunohistochemical detection of CD103 in 11 liver and 10 kidney transplant biopsies with histopathological diagnosis of acute rejection. RESULTS: None of the infiltrates expressed detectable CD103, although positive controls were stained under our conditions. CONCLUSIONS: Failure to detect CD103 in renal biopsies can be related to the early posttransplantation interval (<6 months) corresponding to a first rejection episode. In our hands, immunohistological detection of CD103 was not possible in the infiltrates of acute rejection in liver or kidney transplantation.

Pentoxifylline prevents upregulation of monocyte tissue factor in renal transplant recipients undergoing post-graft complications.

Pentoxifylline (PTX) has been demonstrated to improve graft survival in renal transplant recipients undergoing post graft complications. As activated monocytes are possible initiators of vascular damage through tissue factor (TF) expression, we evaluated the monocyte TF expression and endothelium activation markers in 140 consecutive patients receiving cadaveric kidney grafts, randomized in a double-blind study comparing PTX versus placebo. Monocyte TF expression and plasma von Willebrand factor, tissue plasminogen activator, thrombomodulin and tumor necrosis factor-alpha (TNF-alpha) levels were determined before transplantation and each month after. Additional samplings were realized in case of acute rejection. TF and TNF-alpha expression were significantly modified after graft. In patients with complications, PTX prevented the increase of TF expression at month one, and after rejection episodes. Endothelium activation markers were significantly modified after graft and in patients with complications but PTX had no significant effect on their plasma levels. These results suggest that the protective effect of PTX on graft survival could be related to the prevention of monocyte TF upregulation associated with complications.

Differential effect of cyclosporin A (CyA) on IgE response: role of CyA-induced suppressor cells.

Administration of cyclosporin A (CyA, 30 mg/kg) for the five days following immunization of Brown Norway rats with DNP14-OVA in alum abolished the primary total and specific IgE response, whereas this treatment had no significant effect on the secondary IgE response. On the contrary, with a single injection of CyA on the day of priming, the secondary IgE response only is abolished. The inhibition of the secondary IgE response could be attributed to the induction by a single dose of CyA of nylon wool-adherent spleen cells, as shown by passive transfer experiments. CyA might thus affect the IgE response variously depending on single or repeated administrations.

CD28+ intraepithelial lymphocytes with long telomeres are recruited within the inflamed ileal mucosa in Crohn disease.

Crohn disease is a chronic inflammatory bowel disease that involves all the intestine but predominantly alters the ileum. The disease largely depends on T cells, but the biologic role of intestinal intraepithelial lymphocytes (IEL) in transmural inflammation remains poorly characterized. To address this issue, a comparison of IEL and lamina propria lymphocytes (LPL) isolated from the uninvolved and the inflamed ileal mucosa of Crohn disease patients was performed. More CD8+ IEL (26% versus 8%) from the inflamed ileal mucosa expressed the CD28 receptor and the CD11a integrin than IEL from the uninvolved ileal mucosa, which were mostly CD28-. IEL had longer telomeres in the inflamed than in the uninvolved areas and a TCR Vbeta repertoire more similar to circulating T cells, suggesting that the increased proportion of CD28+ TCRalphabeta+ IEL within the inflamed mucosa is more likely due to recruited lymphocytes from the periphery that populate the epithelial layer than to the acquisition of the CD28 molecule by activated resident lymphocytes. In the uninvolved ileal mucosa, IEL from Crohn disease patients had shorter telomeric lengths than IEL from control patients, suggesting that they have been chronically stimulated. Such perturbation of the IEL population within the ileal mucosa could contribute to the inflammation in Crohn disease.

Treatment of severe Crohn's disease with anti-CD4 monoclonal antibody.

BACKGROUND: Monoclonal CD4 antibodies have been proposed as a new immunosuppressant drug in the treatment of inflammatory bowel disease. We report our experience of treatment with a monoclonal anti-CD4 (B-F5) antibody in severe refractory Crohn's disease. METHODS: Twelve patients with severe refractory Crohn's disease were treated in an open clinical trial. B-F5 was given intravenously at a dose of 0.5 mg. day/kg for 7 consecutive days (patients 1-8). For patients 9-12, B-F5 was given at a dose of 0.5 mg. day/kg on the first day (day 0) and of 1 mg.day/kg on days 1-6. Follow-up examinations were carried out at days 8, 15, 22 and 30. Endoscopic evaluation was performed on days 0 and 30 in eight of 12 patients. RESULTS: Immediately after the first infusion, one patient had dyspnoea and tachycardia requiring cessation of the treatment. Among the 11 patients who received the complete course of treatment, two had prolonged clinical improvement and two had partial clinical improvement. Significant endoscopic improvement was observed in only one patient. No sustained depletion of CD4+ cells could be observed. CONCLUSION: In this uncontrolled open trial, monoclonal anti-CD4 B-F5 antibody was not successful in severe Crohn's disease.

Diagnostic and predictive value of an immunohistochemical profile in asymptomatic acute rejection of renal allografts.

We have retrospectively studied the diagnostic and predictive value of immunohistochemical characterization of adhesion molecules (ICAM-1, CD54, VCAM-1) and HLA-DR antigen in a homogeneous clinical group of 36 patients. Between 1 January 1991 and 31 January 1993, 130 patients received a kidney transplant in our unit. Biopsies of renal allografts were only performed in asymptomatic patients who had graft dysfunction, revealed by an isolated serum creatinine increase. Available frozen samples were included in this study (n = 44). The 35 cases of acute rejection diagnosed by biopsy corresponded to mild acute rejection according to the Banff classification criteria. First, we compared the expression of HLA-DR, ICAM-1 and VCAM-1 to morphological data to determine if the immunohistochemical data improved the histopathological diagnosis when the interstitial infiltrate was mild with slight tubulitis. We also studied the phenotype of infiltrating cells with monoclonal antibodies directed against T helper cells, T cytotoxic-suppressor cells, activated T cells and macrophages. Expression on tubular epithelium and density of each type of cell was graded semiquantitatively. Expression of HLA-DR, ICAM-1 and VCAM-1 was observed on tubular epithelium and endothelium in both acute rejection and other causes of graft dysfunction, limiting its diagnostic value. Activated T cells expressing CD69-AIM (activation inducer molecule) and/or HLA-DR were frequently observed in acute rejection (24/35 (69%) and 25/35 (71%) respectively) but not in other causes of renal dysfunction. We then studied the prognostic usefulness of the immunohistochemical profile in acute rejection. Of 27 patients, 12 had a progressively decreased renal function or returned to dialysis within one year after transplantation while the other 15 had a stable graft function after at least 18 months of follow-up. In the group of bad prognosis (n = 12), corticosteroid-resistant rejection episodes were significantly more frequent (p < 0.01). In this group, nine patients had an overexpression of HLA-DR on tubular epithelium versus one patient in the group of stable graft function (chi 2c = 10.57, p < 0.002). Seven patients included in the group of bad prognosis showed tubular overexpression of both ICAM-1 and VCAM-1 versus one patient in the other group chi 2c = 6.23, p < 0.02). Moreover, patients of the first group had a significantly higher number of interstitial macrophages as compared with those who had stable graft function (chi 2c = 4.87, p < 0.01). Thus, our data show that the immunohistochemical profile studied is of little value in the diagnosis of renal allograft rejection. However, an intense tubular expression of HLA-DR and/or both ICAM-1 and VCAM-1, and a high number of interstitial macrophages are significantly related to unfavorable graft outcome.

Role of anaphylactic antibodies in immunity to schistosomes.

Antibody-dependent cell-mediated cytotoxicity in reinfection immunity to schistosomes in the rat involves either IgG2a anaphylactic antibody and eosinophils or IgE antibody and macrophages. The first system requires two signals, one by the antibody through the eosinophil Fc receptor, another by mast cells through the release of mediators among which is ECF-A. IgE antibody complexed with schistosome antigen binds to an IgE-specific receptor on the macrophage and triggers the cell to release enzymes and superoxide. Immunity in rat schistosomiasis is antibody-dependent, abolished in anti-mu treated neonate rats or by passive serum transfer after selective depletion of either IgG2a or IgE. The two anaphylactic antibody-dependent cell cytotoxicity systems are in a permanent balance in immune rats, eosinophils being blocked by IgG2a immune complexes when this cell is inefficient. Anaphylactic antibodies thus play a key role in triggering and modulating effector cell function.

Comparison of the effects of purified human alpha 1-antichymotrypsin and alpha 1-proteinase inhibitor on NK cytotoxicity: only alpha 1-proteinase inhibitor inhibits natural killing.

While an inhibitory effect on natural killer (NK) cell activity was demonstrated with partially purified alpha 1 Achy, neither highly purified alpha 1 Achy from two healthy donors nor from one patient with giant-cell arteritis, which carries more highly branched glycans, inhibited the NK cytotoxicity. Our purification procedure, based on immunoaffinity chromatography and gel filtration, was not in question since the pure alpha 1-proteinase inhibitor (alpha 1PI) prepared in our laboratory by using a similar procedure continued to inhibit the NK cytotoxicity. If an inhibitory effect not related to antiprotease activity occurs with alpha 1PI, it is surprising that it is not shared by alpha 1 Achy which, like alpha 1PI, belongs to the serpin family and which possesses a strong structural homology with alpha 1PI. Our finding that alpha 1PI is able to affect human NK cytotoxicity while alpha 1 Achy (even with more highly branched glycans) is unable to suggests that events controlling NK activity may involve other enzymes than chymotrypsin-like enzymes.

[Diagnostic value of the assay of beta 2 microglobulin during the monitoring of surgically-treated colorectal cancers. Comparison with carcinoembryonic antigen]. / Valeur diagnostique du dosage de la beta 2-microglobuline au cours de la surveillance des cancers colo-rectaux opérés. Comparaison avec l'antigéne carcino-embryonnaire.

This work presents an evaluation of the diagnostic value of seric beta 2-microglobulin in the follow-up of operated colorectal cancers. Ninety-one patients were operated on with a curative intent between 1976 and 1979. These patients were followed for at least 2 years and divided in 2 groups: a) group NR: 48 patients apparently free of loco-regional recurrence and of distant metastases, b) group R: 43 patients presenting a cancerous relapse. High levels of beta 2-microglobulin were found in 21 patients of group NR (specificity: 56 p. 100) and in 25 patients of group R (sensitivity: 58 p. 100). In the same population, the specificity and the sensitivity of carcinoembryonic antigen (CEA) for the diagnosis of a relapse were 92 p. 100 and 88 p. 100 respectively. No significant statistical correlation was observed between the levels of beta 2-microglobulin and CEA. The sensitivity of the association beta 2-microglobulin + CEA was not superior to the dosage of CEA alone despite its reduced specificity (54 p. 100). These results indicate that the diagnostic value of the dosage of beta 2-microglobulin is inferior to that of CEA and is without interest for the detection of tumoral recurrence in the postoperative follow-up of colorectal cancers.

Individual differences in the in vitro response to cyclosporin A (CsA): possible heterogeneity in the involvement of the CD28-B7/BB1 pathway.

Differences in the response of graft recipients to the immunosuppressive effect of cyclosporin A (CsA) represent a major factor of allograft acceptance. Response to CsA was investigated in vitro in 59 healthy subjects by measuring the inhibition of lymphocyte proliferation and interleukin-2 (IL-2) production. Marked differences were found comparing individuals: 61% of the subjects responded with half inhibitory doses ID50 < 200 ng/ml (responder group), 20% with ID50 within 200-400 ng/ml (intermediate responder) and 19% were non responder with ID50 > 400 ng/ml and sometimes over 1,000 ng/ml. To explain these differences, the CD28-B7, co-stimulatory pathway for T-cell activation was explored since it is the only CsA-resistant pathway known so far. Both responder and non responder individuals showed increased proliferative response and IL-2 secretion by co-stimulation with CD3 and CD28, resulting in increased ID50 by a similar factor. The percentage of CD28+ cells within T-lymphocytes varied markedly among subjects (48.5 +/- 28.9% of the CD8+ cells). However we could not correlate the inter-individual variation of sensitivity to CsA to the size of the CD8+CD28+ T cell subset nor to divergent response to CD3 and CD28 co-stimulation.